This invention relates to a novel method of assembling a mask-panel assembly of a shadow-mask cathode-ray tube.
Most commercial shadow-mask cathode-ray tubes comprise a glass faceplate panel including a viewing window. Such tubes, which are used in color-television receivers, include also a luminescent screen supported on the inner surface of the viewing window, and a shadow mask mounted on the panel and located at a predetermined, precisely-spaced position with respect to the inner surface of the viewing window.
In one method for assembling such tubes, the panel includes integral glass sidewalls extending from the periphery of the window, with metal studs implanted in the inner surface of the sidewalls. Metallic springs are permanently mounted on the mask by welding and are detachably mounted on the studs. Mounting the mask includes the mounting of the springs to the mask and to the studs, and includes also a setting of the precise spacing q of the mask from the inner surface of the window. The setting of the q, or q-setting as it is called in the art, is adequately described in the prior art; for example, in U.S. Pat. Nos. 3,296,625 to T. M. Shrader et al and 3,701,193 to F. R. Ragland. Most q-setting involves the positioning and removal of a spacer between, and in physical contact with, the panel inner surface and the mask during the final welding step of mounting the springs to the mask. Also, measuring devices may be temporarily placed between the mask and window surface to check the spacing.
The panel with the mask properly spaced from the window and mounted within the panel is referred to as a mask-panel assembly. This mask-panel assembly may be baked for such temperatures and times as to dimensionally stabilize the assembly, as described in U.S. Pat. No. 3,335,479 to A. M. Morrell, after which the luminescent screen is deposited on the inner surface of the window by a photographic technique, usually using the mask as a photographic master.
During the steps involved in mounting the mask and the subsequent steps for the measuring of q, the inner surfaces of many of the viewing windows may be abraded or bruised, which damages usually manifest themselves as clearly-visible optical blemishes in the viewing field of the window, usually near the edges of the viewing windows. Such abrasions and bruises may result from accidental bumping or rubbing of the inner window surface by solid objects or from the misuse of spacers and/or measuring devices used during and after mounting.